There are a lot of spiders they could add. There are also a lot of mystical animals they could add such as a Cockatrice and a Basilisk. (no not the type of Basilisk in Harry Potter. That is just a giant snake.)

So here is another list of mythical animals:
Cockatrice
Gryphon
Basilisk
Cracken
Chimera

There is probably a lot more Mythology animals that are not half human or what ever,but I cannot think of them.